Solid oxide fuel cells for ammonia synthesis and energy conversion

Abstract

Fuel cells are electrochemical devices that convert the chemical energy of a fuel and an oxidizing agent into electricity, producing water as a byproduct. This work demonstrates the use of solid oxide fuel cells (SOFCs) to produce ammonia with cogeneration of electrical power. Ammonia synthesis from an operating SOFC is achieved by supplying humidified air and fuel (hydrogen or methane). The ammonia synthesis via the electrochemical promotion of catalysis (EPOC) becomes feasible with a zirconium oxide-based O²⁻ conducting electrolyte (ScSZ). Significant improvement in the Faraday efficiency and electrical efficiency (Λ > 2) is observed in this system. A high rate of ammonia production, 8.6 × 10⁻⁹ mol cm⁻² s⁻¹, is attained when the cell operates with 14% humidified air and methane at 730 °C. This ammonia synthesis approach could be competitive with the Haber–Bosch process.